# Impacts of Gate Recess and Passivation on AlGaN/GaN High Electron Mobility Transistors

## Abstract

In this study, the impacts of gate recess and passivation on AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. The trap-related characteristics were studied in detail by several different measurements including dc current–voltage, current collapse, gate lag, and flicker noise characterizations. With a Cl2/Ar-recessed gate, drain current collapse factors ($\Delta I_{\text{max}}$) of ${\sim}37.5$ and ${\sim}6.9$% were observed before and after SiN passivation. The gate lag measurements showed that the lagging phenomena almost disappear with SiN passivation for both Cl2- and Cl2/Ar-recessed devices. However, the flicker noise measurements revealed distinct noise levels of devices with different processes even after passivation. As the gate voltage ($V_{\text{G}}$) changed from 2 to $-4$ V, the devices recessed by Cl2 exhibited lower drain noise current densities ($S_{\text{ID}}/I_{\text{D}}{}^{2}$ ranging from $2.8\times 10^{-14}$ to $1.7\times 10^{-12}$ Hz-1 at 1 kHz) than those etched by Cl2/Ar mixture gas ($S_{\text{ID}}/I_{\text{D}}{}^{2}$ ranging from $6.3\times 10^{-14}$ to $6.0\times 10^{-12}$ Hz-1 at 1 kHz), whereas the devices without the recess process showed the lowest noise levels ($S_{\text{ID}}/I_{\text{D}}{}^{2}$ ranging from $2.8\times 10^{-15}$ to $1.3\times 10^{-13}$ Hz-1 at 1 kHz). It was found that $S_{\text{ID}}/I_{\text{D}}{}^{2}$ increased monotonically when $V_{\text{G}}$ changed from 2 to $-4$ V. A bias dependence of the $1/ f^{\gamma}$ slope $\gamma$ was observed, and a relatively large variation in the range of ${\sim}1.1$ to 1.6 was found for devices recessed by Cl2/Ar mixture gas. The number fluctuation model was employed to explain the observed trends. The results also indicated that the surface traps play an important role in these devices.

## Journal

• Jpn J Appl Phys

Jpn J Appl Phys 46(2), 478-484, 2007-02-15

INSTITUTE OF PURE AND APPLIED PHYSICS

## References:  19

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## Codes

• NII Article ID (NAID)
10018544630
• NII NACSIS-CAT ID (NCID)
AA10457675
• Text Lang
EN
• Article Type
ART
• Journal Type
大学紀要
• ISSN
0021-4922
• NDL Article ID
8650769
• NDL Source Classification
ZM35(科学技術--物理学)
• NDL Call No.
Z53-A375
• Data Source
CJP  NDL  JSAP

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